Yes, it’s the dead of winter, but in six weeks—spring. Now’s the time to cultivate. This crocus flower is bursting from a windowsill gardening kit available at Brooklyn Farms, a new hydroponic supply store in Cobble Hill. The benefits of hydroponic: bigger plants and better crop yields. The kit includes clay pellets (in place of soil), a two-gallon reservoir, plant food, and, most important, easy-to-follow instructions ($89.95; 521 Hicks St., at Degraw St.; 347-725-3491).